Heat exchange device



Patented May 14, 1940 UNITED STATES- PATENT OFFICE HEAT EXCHANGE DEVICE Fredric H. Monson, Minneapolis, Minn. Application November 12, 1938, Serial No. 239,899

3 Claims.- v((11. 257-241) This invention relates broadly to heat exchange apparatus and more particularly to an improved type of boiler for use with heating systems of the type cooperable with heat engines having an exhaust line from which heat is extracted for transfer to desired points.

Viewed from another aspect, it is an important object of the invention to provide an improved boiler constructed and arranged to be mounted in the exhaust line of a heat engine, for example an internal combustion engine such as commonly used in automotive vehicles, the boiler forming part of a heating system for the vehicle.

Another object is the provision of a boiler of elongated form having inlet and outlet openings at one end and designed to be installed in an elongated exhaust pipe by the provision of a small opening in the side of the pipe, through which the boiler is inserted, the boiler being provided with a cover plate constituting a closure for the opening cut in the pipe.

Another object is the provision of a boiler of the type heretofore characterized and which is constructed to expand and contract in the direction of its length and consequently in the direction of the length of the exhaust line, the boiler expanding, moreover, independently of the piping by means of which it is connected in the heating system.

Still another object is the provision of 2. iongitudinally expansible boiler arranged and constructed to fiex in a lateral direction against the walls of the exhaust pipe, whereby to alter the heat exchange under certain conditions.

Yet another object is the provision of a boiler including a pair of elongated and collaterally extending conduits expansible in the direction of their length and each attached at opposite ends by a common juncture with anintake and outlet conduit, the conduits being supportably attached to a mounting member constructed to provide a closure for an opening in an elongated exhaust pipe into which the boiler is inserted.

Other objects and advantages of the invention reside in certain details of construction, form, location, and operation of the apparatus described hereinafter in view of the annexed drawing, in which: a

Fig. 1 is a perspective layout of a heating system incorporating the improved heat exchange device;

Fig. 2 is an enlarged fragmentary cross section through the exhaust pipe of Fig. 1, as viewed along line 22 therein;

Fig. 3 is a cross section along line 3--3 of Fig.

2; while Fi'g. 4 is a transverse section through the exhaust line and boiler structure, as viewed along line 4-4 of Fig. 3.

The invention is especially adapted for use in a heating system for automobiles andthe like connected in this instance with. a muiiier I 2, .ex-

haust gases passing from the manifold connections ll toward and through the muffler l2.

The improved boiler I 3 is of elongated form and is disposed within the exhaust line or pipe l between its ends by means hereinafter to be described.

Referring conveniently between Figs. 2 and 3;

a preferred embodiment of the invention includes a pair of elongated conduits l5 and I6 normally" arranged to extend collaterally or in parallel side by side relation, and each connected at one end to a branch I! or I8 of a junction or union with an exhaust conduit 20, the opposite ends 2| and 22 of the expansible conduits being connected in common with a U-shaped union 23 which in turn connects with an inlet conduit 24. The inlet conduit 24 extends collaterally with the conduits l5 and I6 and is preferably joined to the exhaust or steam conduit 20 as at 25, this juncture being preferably effected by welding or brazing, and the juncture between the two pipes or conduits being provided with an .opening 26 which provides a by-pass between the intake and exhaust sides of the boiler for purposes which will hereinafter appear.

Near their joined portions 25, the intake and exhaust feed lines 20 and 24 are extended through a mounting plate 30 (see also Figs. 1 and 4) and are rigidly attached to the same by means of welding or brazing 3|, the pipes or conduits 20 and 24 continuing on through the plate 30in their respective extensions 20' and 24' for connection in the heating system.

The piping 20 and 24 is preferably flexible, for example a heavy copper tubing, and this provision, in conjunction with the flexible nature of the boiler conduits themselves. results in a flexible unit which is very readily installed in commonly used forms of exhaust line, this character u of the construction constituting one of the important features of the invention.

In the illustrative installation, the exhaust line III is of cylindrical form and the mounting plate 30 is therefore constructed in semi-cylindrical contour so as to fit snugly against the outer surface of the exhaust pipe 10 when the boiler is mounted in operative position.

Installation of the boiler is very simple and is accomplished by cutting an opening 32 (Figs. 2 and 3) in the side of the pipe Hi, the elongated boiler unit thereafter being inserted through this opening and the mounting plate 30 fitted flush against the opening so as to cover the same. Thereafter, suitable means in the form of the screw clamps 33 are secured around the mounting plate 30 to clamp the latter firmly against the exhaust pipe, thus closing the opening 32 and also positioning the boiler structure in substantially co-axial alignment with the pipe on the interior thereof, the relative disposition, length, and means of attaching the pipes 20 and 24 to the boiler conduits l5 and I6 being such as to maintain the boiler in normally spaced relation to the inner sides of the exhaust pipe and providing an adequate degree of rigidity to prevent rattling of the boiler against'the sides of the exhaust pipe.

An important feature of the invention is the longitudinal expansibility of the boiler tubes or conduits themselves. These tubes or members I5 and I6 are preferably formed from elongated sections of copper or similar tubing constructed with a plurality of circumscribing,integral, hollow flanges 35 (Fig. 3) formed in the manner of a bellows. This-constructionresults not only in an axial flexibility or expansibility of the conduits, but also greatly increases the radiating surface for a given length of pipe. Moreover, in addition to axial or longitudinal flexibility, the conduits l5 and 16 are also capable of bending or lateral flexing, this feature also being of advantage in the operation of the device, as will appear hereinafter.

i The heating system in which the improved heat exchange device is employed may include a reservoir or water tank 38 connected by a feed conduit 39 to a power-driven pump 40 which communicates through-acheck valve 41 with the extension 24 of the feed pipe 24 leading into the boiler. The steam or exhaust line 20 fromthe boiler communicates through its extension 20 with a honeycomb type radiator 42 adapted for installation in the cab of a vehicle and provided with the usual blower means for effecting forced circulation of air relative to the radiator.

Assuming the automobile'or other heat engine to be running with exhaust gases traversing the pipe I'll, the heating system is started by energizing the pump 40 to force water from the tank 38 past the check valve 4| and through the extension 24' into the feed line 24 for circulation through the branch 23 at the right-hand end of the boiler and through the collaterally extending, expansible boiler tubes Hand 16.

' Should the incoming water be cold as it leaves the tank 38, its temperature will be gradually raised as it progresses through the feed line 24'-24 due to heating of the portion 24 of the feed line within the pipe. The degree to which the incoming water will thus be preheated will vary. However, the construction of the novel boiler is such that even though the incoming water be at a considerably lower temperature than the boiler tubes l5 and it, no injury will result because of the expansible nature of the tubesand the fact that they will shift longitudinally to meet any differential between the temperature of the incoming water and the temperature of the tubes themselves. If the differential is too great the tubes will bow.

Due to the very extensive surface area of the flanged expansible tubes I5 and IS, the latter will quickly absorb large amounts of heat from the exhaust gases traversing the exhaust line, and the incoming water will quickly be converted to steam which is fed back through the branches I1 and I8 in the union IB'and into the exhaust line 20 for distribution through the radiator.

The by-pass opening 26 between the intake and exhaust sides of the boiler line, permits a small quantity of water to be drawn into the exhaust line periodically with the rise and fall of pres sures in the system to moisten the steam moving toward the radiator. Condensed water in the radiator is returned by a conduit 43 through a steam trap 44 to the upper'part of the reservoir 38.

The expansible tubes l5 and I8 are preferably provided with a heavy oxide coating to protect the metal thereof against oxidation in the exhaust gases, the coating being preferably formed by oxidation of themetal itself, so that it is flexible and safe from injury or rupture due to the expansion and contraction of the conduits.

Another important feature of the invention is the automatic regulation of which the device-is capable when excessive amounts of heat within the pipe l effect the maximum expansion of the conduits I and I6. Due to their lateral flexibility or bending quality, the conduits I5 and It will bow in a lateral direction against the inner sides of the exhaust line It! and into the dotted line position indicated in Fig. 2 when the temperature exceeds a predetermined value, and, as a result, provide for relatively rapid contactheat-exchange between the flanges on the boiler tubesand the walls of the pipe in, thus shunting a portion of the heat energy from the boiler for dissipation into the pipe In.

In the event that cold water is supplied to the boiler at a time when the latter is excessively hot, this water must first traverse the conduit 24 before it enters the bellows portion of the heat exchanger. Because of the limited cross section of this conduit 24, and because its temperature is the same as the bellowed portion of the device, it will flash a certain portion of the entering water to steam, thereby providing back pressure and obstruction to further flow, therefore temporarily reducing the rate of flow of the solution through the heat exchanger.

The foregoing action is effective through the entire length of both conduit 24 and the bellows portion of the heat exchanger, thereby limiting the supply of fluid to the heat exchanger until such a time as the temperature, pressure, and heat exchange can strike a balance and thus prevent the formation of excessive back pressure. This is an important feature of this heat exchanger.

,Moreover, due to the fact that the heat exchanger is installed with the fluid inlet to the bellowed portion closest to the manifold or source of heat, the fact that the boiler might be filled with water before initial heating or starting of the engine, will not be disadvantageous because changer through conduit 20 and thence through the rest of the system and back to the reservoir, and at the same time prevent a further supply of solution through conduit 24 until the pressure has been reduced in the heat exchanger and the remainder of the circuit.

From the foregoing it will be seen that certain inherent characteristics of the design of this boiler absolutely prevent formation of excessive pressures regardless of the condition which might exist within the boiler or system, hot or cold.

Another important feature is the fact that the boiler when in operation is maintained tight 1 against the exhaust pipe, due both to pressure in the bellows, and the thermo-expansive action of the combination of two lengths of bellows connected to conduits 20 and 24 and all supported as shown within a restricted area, thus preventing rattle and the removal of oxide formation.

The objects and advantagesnof the invention may be accomplished by changes in the construction, form, and location of the parts and arrangement specified herein for purposes of illustration, all without departing from the spirit and scope of the invention as defined by the appended claims which are to be broadly interpreted to include all equivalent forms and arrangements.

Having thusdescribed my invention, what I claim as new and desire to protect by Letters Patent is:

1. A heat exchange device for use with an elongated exhaust gas pipe, said device comprising a plurality of elongated boiler tubes having integrally i'ormed bellows flanges providing for expansion of said tubes in the direction of their length and permitting said tubes to bow laterally of their length, an intake line connected in common juncture with the corresponding ends of each of said tubes and led back toward the op- 4 posite end of said tubes, an exhaust line connected in common juncture with said opposite ends of the tubes, said heat exchange device including said boiler tubes being disposed within said exhaust pipe, said intake line being connected with a source of water for generation of steam within the tubes, said exhaust line being connected with steam utilization means, means rigidly securing said intake and exhaust lines against substantial displacement longitudinally, said tubes being normally disposed in spaced relation to the inner wall portions of said exhaust pipe and being adapted to bow for contact with said inner walls when a predetermined temperature condition exists in said tubes and said pipe.

2. In an automotive heating system including an exhaust duct, a boiler structure comprising a plurality of collaterally extended boiler tubes of flexible construction adapted to bend in a direction lateral of their length as a result of expansion longitudinally, intake conduit means connected to one end of all of said boiler tubes, and exhaust conduit means connected to the opposite ends of all of said boiler tubes, said boiler tubes being adapted for insertion in said exhaust duct, said conduits being adapted for connection in said heating system, and means for rigidly securing said intake and exhaust conduits against substantial displacement in a; direction longitudinally of said boiler tubes and exhaust duct whereby the opposite ends of the boiler tubes will be disposed in substantially fixed positions to cause said tubes to bow laterally as a result 01 expansive forces set up therein when heat is applied thereto, said boiler tubes being arranged within said pipe so as to expand into firm engagement with the inner walls of said exhaust duct to prevent movement of the boiler structure within the exhaust duct when hot exhaust gases are passing therethrough.

3. In a heat exchanging device, a conduit through which hot gases are passed and a boiler tube structure" of generally elongated construction fitted into said conduit and comprising a plurality of elongated and longitudinally expan- -sible boiler tubes arranged and constructed to flex laterally, and means providing conduit connections with the opposite ends of said tubes for circulating fluids therethrough and arranged to secure said ends in substantially fixed condition whereby to cause said tubes to bow laterally against the inner sides of said hot gas conduit in response to expansive eflorts in said tubes resulting from the heating thereof by said gases.

FREDRIC H. MONSON. 

